Mapping of the pneumococcus chromosome: differences between recipient strains varying inhexproperty and the location of theopt-r2gene

Abstract

SUMMARYTransformation studies in pneumococcus had shown that loci determining the resistance to erythromycin and streptomycin were unlinked when strain Cl3 was recipient but linked when strain SIII-I was recipient. This phenomenon also applies to other pairs of markers studied in these two recipients, no matter whether the transforming DNA was derived from strain Cl3 or strain SIII-I. Other differences between the two recipient strains were also revealed. Whereas competent cultures of strain Cl3 were composed of all competent cells, which was in agreement with previous reports of pneumococcal cultures, strain SIII-I normally gave a maximum average of 28% competent cells. Strain SIII-I was unstable, since on repeated sub-culturing the competence peak profile changed and the value of ‘fcq’ increased. These properties were reflected in the twohex−strains 401 and R6x which were found to be similar to the ‘altered SIII-I’ strain. The results from the linkage studies have been applied to the chromosome map and have placed theopt-r2gene in thestr-r41-containing chromosome arm.